German Patent Publication (DE) 3,205,032 discloses a position detector of the type described above, whereby the ruler is constructed of a plurality of sections, including magnetic sections and nonmagnetic sections, whereby all the sections have the same length. These sections are arranged in alternate fashion along the length of the ruler, one behind the other. The ruler moves relative to a sensor coil or winding, thereby inducing in the coil or winding respective signals. The known device is merely suitable for ascertaining the relative position of a magnetic ruler section within the sensor coil. As a result, larger distances can be measured only in incremental fashion or it is possible to arrange two such devices in parallel, one of which has a ruler with sections that provide a coarser subdivision, in other words, the sections are longer than the ruler sections in the other detector. Another disadvantage of these known magnetically absolute measuring detectors is seen in that they are rather bulky relative to the maximally measurable length. Still another drawback of conventional measuring devices of this type is seen in that they must always be calibrated again when they are placed in operation to eliminate the measuring error, or at least reduce the measuring error of these devices. The recalibration is necessary because there is no fixed relationship between the movable member and the stationary member of the conventional device, i.e. there is no embodiment of a measure.
It is also generally known to encode distance information in a detector as, for example, disclosed in European Patent Publication 0,078,892 (Schmitt).